1. Field of the Invention
The present invention relates to a vehicle generator motor having plural sets of armature windings, and a method of controlling the vehicle generator motor.
2. Description of the Related Art
In order to obtain a sufficient output (power) and reduce noise under operation in a generator motor such as a three-phase synchronous motor or a generator, there has been proposed an apparatus including plural sets of armature winding systems each of which comprises three-phase armature windings (hereinafter referred to as three-phase windings) and an inverter device for controlling the three-phase windings. Furthermore, it has been proposed that when the load of the generator motor is small, the operation of some of the plural sets of armature winding systems is stopped thereby reducing the switching loss at the inverter device and enhancing the efficiency, or when some of the armature winding systems fail to operate properly, the outputs of the residual armature winding systems are increased, thereby bringing a fail-safe function (for example, JP-A-5-103497).
As described above, if a plurality of armature winding systems are provided, the output can be increased as described above. However, when a generator motor and an internal combustion engine are connected to each other, particularly when they are connected to each other through a belt, the internal combustion engine would be broken or the lifetime of the belt would be shortened if the output torque increases excessively.
Furthermore, the electrically generated output at the generator motor is normally supplied to a battery and a vehicle load. The vehicle load varies in accordance with the environment of the vehicle (for example, an air conditioner is turned on/off or the like) and thus it is not fixed. Therefore, the power generation amount of the generator motor is adjusted in conformity with required power generation amount, however, the battery normally absorbs variation of power generation amount which the generator motor cannot follow. However, when the charging capacity of the battery is large, the battery has no margin of absorbing surplus power generation amount, and thus the battery is excessively charged, which adversely affects the lifetime of the battery.